The Grand Mosque Seizure on November 20, 1979, was an armed attack and takeover by armed Islamic fundamentalist dissidents of the Al-Masjid al-Haram in Mecca, Saudi Arabia, the holiest place in Islam.

In the 1960s Osama bin Laden's half-brother Mahrous bin Laden joined a rebel group opposed to the Saudi government. With his assistance, in 1979 the rebels smuggled weapons into Mecca, Saudi Arabia, using trucks belonging to the bin Laden family company. 500 rebels then seized the Grand Mosque in Mecca (sic), Islam's holiest mosque in its holiest city. They try, but fail, to overthrow the Saudi royal family. All the men who took part are later beheaded except Mahrous. Eventually he is released from prison because of the close ties between the bin Ladens and the Saudi royal family. Mahrous apparently abandons the rebel cause and joins the family business. He is eventually made a head of the Medina branch and a member of the board. He will still hold these positions on 9/11. But a newspaper reports that "his past [is] not forgiven and most important decisions in the [bin Laden family business] are made without Mahrous' input."

Sunday Herald (Glasgow), 10/7/2001
Ha'aretz, 12/18/2002
New Yorker, 11/5/2001